1. Field of the Invention
This invention relates to a hydrostatic drive system with a pump and at least one consumer that can be controlled by a control valve actuated by control signals. A precharge device that generates a precharge pressure is located in a reservoir line that leads from the control valve to a reservoir and can be pressurized as a function of the control signals from the control valve.
2. Technical Considerations
On some drive systems, a precharge device is provided in the reservoir line to generate an elevated precharge pressure in the reservoir line under certain operating conditions. This precharge pressure can effect a recharging of pressure fluid from the reservoir line into the admission side of the consumer. As a result of which, any underfilling and cavitation of the consumer can be prevented.
A similar drive system is described in DE 197 09 958 A1. In that case, the precharge valve located in the reservoir line can be set to an elevated precharge pressure with an increasing control signal of a control valve. When the control valve is actuated, a negative load is controlled by the control signal. As a result, under operating conditions in which the consumer controls a negative load, a recharging from the reservoir line into the admission side of the consumer can be effected.
However, in drive systems of this type, operating conditions can also occur in which a recharge is necessary in the event of a reduction of the control signal of the control valve to decelerate the consumer. With these known drive systems in which the precharge device is pressurized as the control signal increases in the direction of an increase of the precharge pressure, a recharge cannot be achieved under such operating conditions.
Therefore, it is an object of the invention to provide a hydrostatic drive system of the general type described above but which makes recharging possible when a consumer is decelerated.